Area Forecast Discussion
Issued by NWS Medford, OR

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000
FXUS66 KMFR 071642
AFDMFR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
842 AM PST SUN FEB 7 2016

.UPDATE...WITH HIGH PRESSURE IN CONTROL, THERE IS LITTLE OF MAJOR
CONCERN THIS MORNING. FOG HAS BEEN THE PRIMARY FORECAST PROBLEM,
MAINLY IN THE WEST SIDE VALLEYS, ALTHOUGH SOME AREAS EAST OF THE
CASCADES HAVE FORMED THIS MORNING AS WELL. HAVE ADJUSTED SKY AND
WEATHER PARAMETERS TO ACCOUNT FOR CURRENT OBSERVATIONS, BUT MADE
NO OTHER CHANGES TO THE MORNING PACKAGE.

FOR MORE INFORMATION, SEE THE PREVIOUS DISCUSSION BELOW. -BPN


&&

.AVIATION...FOR THE 07/12Z TAF CYCLE...VALLEY LOW CLOUDS AND FOG
ARE EXPECTED THIS MORNING BOTH EAST AND WEST OF THE CASCADES. THIS
MAY BE SLOW TO BURN OFF THROUGH THE MORNING AND EARLY AFTERNOON,
BUT MOST AREAS SHOULD EVENTUALLY RETURN TO VFR. CLEAR SKIES WILL
REMAIN UNTIL TONIGHT, WHEN VALLEY FOG AND LOW CLOUDS RETURN.
EXPECT MVFR/IFR AND SIGNIFICANT MOUNTAIN OBSCURATIONS THROUGH THE
NIGHT AND INTO THE MORNING. -BPN

&&

.MARINE...UPDATED 830 PM PST SUN FEB 7 2016...LIGHT SOUTHEAST
WINDS ARE EXPECTED TO TURN NORTH TO NORTHEAST THIS AFTERNOON AND
EVENING BUT REMAIN LIGHT....THEN LIGHT NORTHEAST TO EAST WINDS
CONTINUE ON MONDAY. WINDS WILL SHIFT TO SOUTHERLY ON TUESDAY AS
HIGH PRESSURE MOVES INLAND. ADDITIONALLY...STEEP SEAS ARE EXPECTED
TO DEVELOP MONDAY AS A LONG PERIOD WEST SWELL OF AROUND 10 FEET
AT 16 SECONDS BUILDS INTO THE WATERS.

A FRONT MAY APPROACH THE COASTAL WATERS ON WEDNESDAY THEN MOVE
INTO THE WATERS THURSDAY. MODELS SHOW VARIABILITY WITH THE
STRENGTH AND TIMING OF THIS FRONTAL SYSTEM, THUS CONFIDENCE IS
LOW ON DETAILS FOR WAVE AND WIND FORECASTS DURING THIS PERIOD.
OVERALL, EXPECT AN INCREASE IN SEAS WEDNESDAY AND THURSDAY, WITH
THE POTENTIAL FOR SMALL CRAFT WINDS AND STEEP SEAS. ANOTHER STEEP
LONG PERIOD SWELL MAY MOVE INTO THE WATERS LATE THURSDAY AND
FRIDAY. -BPN/SVEN


&&

.PREV DISCUSSION... /ISSUED 100 AM PST SUN FEB 7 2016/

DISCUSSION...07/00Z NAM/GFS IN.

THE NORTHERN HEMISPHERIC PATTERN CONTINUES TO SHOW A NEAR
TEXTBOOK 5 WAVE PATTERN AROUND THE GLOBE WITH MODERATE AMPLITUDES.
THIS PATTERN WILL CONTINUE BUT LONGITUDINAL FLOW WILL
INCREASE...CREATING A MORE BLOCKY PATTERN AROUND THE GLOBE.
THE PATTERN WILL REMAIN PROGRESSIVE...BUT WILL SLOW DOWN OVER THE
NEXT SEVERAL DAYS AS A STRONG RIDGE BUILDS OVER THE EASTERN
PACIFIC AND WESTERN NORTH AMERICA.

THE RIDGE WILL MOVE VERY SLOWLY EAST...AMPLIFYING THROUGH MONDAY.
BUT THAT TIME IT WILL BE DIRECTLY OVER THE MEDFORD CWA. DRY
CONDITIONS AND LOW LEVEL OFFSHORE FLOW WILL PERSIST INTO TUESDAY
AND TEMPERATURES WILL WARM TO ABOVE SEASONAL VALUES...ESPECIALLY
ALONG THE SOUTH COAST AND OVER THE RIDGES. MOSTLY CLEAR SKIES WILL
PREVAIL OVER MOST OF THE AREA. THE EXCEPTION WILL BE THE WEST SIDE
VALLEYS...WHERE WARM AIR ALOFT WILL STRENGTHEN INVERSIONS...WHICH
WILL TEND TO KEEP CLOUD COVER AND COOLER AIR TRAPPED OVER THOSE
AREAS. SINCE THIS IS LATE IN THE SEASON FOR SUCH PATTERNS...THE
LOW CLOUDS AND FOG ARE EXPECTED TO BURN OFF IN THE AFTERNOONS AND
EVENINGS.

USUALLY AIR STAGNATION IS A CONCERN IN A PATTERN LIKE THIS...BUT
GIVEN THE EXPECTED AFTERNOON MIXING...WILL NOT ISSUE ANY
ADVISORIES AT THIS TIME.

THE RIDGE WILL CONTINUE TO DRIFT EAST...AND WEAK SHORT WAVES
EJECTING FROM THE UPSTREAM TROUGH WILL START TO MOVE OVER THE
AREA WEDNESDAY. TYPICALLY THE FIRST SHORT WAVE AFTER A RIDGE HAS
LITTLE EFFECT OTHER THAN HERALDING THE END OF OFFSHORE LOW LEVEL
FLOW...AND THESE LOOK TOO WEAK TO DO MUCH OF ANYTHING. MORE SHORT
WAVES WILL FOLLOW THOUGH...PUSHING PROGRESSIVELY STRONGER FRONTS
ONSHORE. SO...PRECIPITATION WILL LIKELY RETURN SOMETIME IN THE
SECOND HALF OF NEXT WEEK. THE BEST GUESS FOR THE NEXT SIGNIFICANT
ROUND OF PRECIPITATION RIGHT NOW IS THURSDAY NIGHT...ALTHOUGH A
WEAK FRONT MAY BRING SOME LIGHT RAIN TO THE COAST AS EARLY AS
WEDNESDAY NIGHT.

&&

.MFR WATCHES/WARNINGS/ADVISORIES...
OR...NONE.

CA...NONE.

PACIFIC COASTAL WATERS...NONE.

$$

BPN/SBN/JRS


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